Peptide hormones are widely used in medical practice and since they can be produced by recombinant DNA technology it can be expected that their importance will increase also in the years to come. When native peptide hormones or analogues thereof are used in therapy it is generally found that they have a high clearance rate. A high clearance rate of a therapeutic agent is inconvenient in cases where it is desired to maintain a high blood level thereof over a prolonged period of time since repeated administrations will then be necessary. Examples of peptide hormones which have a high clearance rate are: ACTH, corticotropin-releasing factor, angiotensin, calcitonin, insulin and fragments and analogues thereof, glucagon, glucagon-like peptide and analogues and fragments thereof, IGF-1, IGF-2, enterogastrin, somatostatin, somatotropin, somatomedin, parathyroid hormone, thrombopoietin, erythropoietin, hypothalamic releasing factors, prolactin, thyroid stimulating hormones, endorphins, enkephalins, vasopressin, oxytocin, opiods and analogues thereof, superoxide dismutase, interferon, asparaginase, arginase, arginine deaminase, adenosine deaminase and ribonuclease.
Although it has in some cases been possible to influence the release profile of peptide hormones by applying suitable pharmaceutical compositions this approach has various shortcomings and is not generally applicable. Accordingly, there still is a need for improvements in the field of administration of peptide hormones.